NovaEvacuate: Remove bashism

Commit 143864c694 introduced a bashism, this commit fixes it by using a
pipe instead of a process substituion.
As pipes can only carry standard output, we first redirect stderr to
stdout, pipe it to grep, then redirect the filtered output to stderr again.

Closes-Bug: #1555020
Change-Id: Ia0a5cc7130ae8029bb348c0f439f2c92f247d1e6
Signed-off-by: Norbert Illes <norbert.e.illes@ericsson.com>

ocf/NovaEvacuate

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/sh
 #
 #
 # NovaCompute agent manages compute daemons.
@@ -256,7 +256,7 @@ evacuate_monitor() {
 
     handle_evacuations $(
         attrd_updater -n evacuate -A \
-            2> >(grep -v "attribute does not exist" 1>&2) |
+            2>&1 | grep -v "attribute does not exist" |
             sed 's/ value=""/ value="no"/' |
             tr '="' '  ' |
             awk '{print $4" "$6}'